Use `airshipctl plan run` in `multi-tenant` Type Gating

[lb4368]

Proposed change
Update gating for multi-tenant type to use airshipctl plan run for deployment rather than running individual phases.

This issue is split off #166 to address the multi-tenant type if/when it becomes a priority. Currently gating for the virtual-multi-tenant site has be moved to experimental (https://review.opendev.org/c/airship/treasuremap/+/800299).

Initial PS for the multi-tenant gating: https://review.opendev.org/c/airship/treasuremap/+/796028

[sanjib-35]

please assign to me

[lb4368]

@sanjib-35 Based upon the PTG discussion, the multi-tenant type is deprecated. This issue should probably be canceled. You may want to select a different issue to work on.